This application addresses broad Challenge Area (04) Clinical Research and Specific Challenge Topic, 04-DA-102: A New Look at Longitudinal Data. Prior research has consistently indicated that adolescents who are at risk for developing substance use disorders exhibit externalizing behavior problems, including higher levels of conduct problems (e.g., oppositional behavior, aggression, delinquency) and attention-deficit/hyperactivity (ADHD) symptoms (i.e., inattention, hyperactivity, impulsivity). Recent research has identified a phenotypic vulnerability to disinhibitory psychopathology, called the externalizing spectrum, which is believed to underlie the development of substance use, problems, and disorder during adolescence and adulthood, and externalizing behavior problems that occur across the lifespan (ADHD, oppositional defiant disorder, conduct disorder, and antisocial personality disorder). Yet developmental models of the externalizing spectrum have not been tested, nor has the emergence of substance use and problems within the externalizing spectrum been examined. Given the public health costs associated with substance use, it is imperative to study the process by which substance use disorders emerge and where, when, or with whom it is possible to intervene in order to prevent the development of substance use problems and disorder. The proposed study will capitalize on an extensive longitudinal data set, the Fast Track project, to examine the relationships between different indicators of the externalizing spectrum from childhood to late adolescence. Fast Track was a multisite, longitudinal study that conducted annual evaluations from kindergarten to age 20 in a community sample of children (n = 754) at high risk for serious conduct problems, who were identified from a screening sample of 9,454 children. The first goal of the proposed research is to use the screening and longitudinal samples to develop a developmentally sensitive model of the externalizing spectrum (including substance use) within three developmental periods (childhood, early adolescence, and late adolescence), with a specific focus on testing whether the psychometric structure of the externalizing spectrum is consistent across time, sex, race, and neighborhood setting (urban vs. rural). The second goal is to test whether the externalizing spectrum can be represented by a single higher-order factor across developmental periods, and to determine whether the underlying externalizing spectrum is best characterized as categorical (i.e., qualitatively distinct pathways of development) or continuous (i.e., continuum of externalizing problems throughout adolescence). Ultimately, the results from these secondary data analyses will provide insight into potential targets for the prevention and treatment of substance use, problems, and disorders. This project will increase understanding of how the "externalizing spectrum" of behaviors is expressed from childhood through late adolescence. It will also examine how substance use, problems, and disorder emerge as part of the externalizing spectrum across this developmental period. This has important implications for designing more effective preventive and treatment interventions for substance use and related problems.